In a convertible roll stand of the type described in the commonly owned and concurrently filed patent application Ser. No. 657,415 now U.S. Pat. No. 4,563,888 a six-high roll stand is described wherein the working rolls can be displaced horizontally in the workpiece-travel direction from a position with the working-roll axes coplanar with the backup-roll axes to a position with the working-roll axes slightly downstream from this plane. This downstream position is employed when very small diameter working rolls are used, in installations for rolling very hard, thin, or wide steel strip, and in conjunction with some sort of downstream lateral bracing of these slender working rolls. For a fuller discussion of these systems, see, in addition to the above-mentioned patent application, pages 309-314 of Herstellung von kaltgewalztem Band (Verlag Stahleisen, Dusseldorf; 1970).
Such an installation comprises, as described in the above-mentioned patent application, a frame having a pair of sides spaced apart transversely of a workpiece travel direction and formed with respective throughgoing windows aligned transversely of the direction and a pair of vertically spaced traverses extending horizontally perpendicular to the direction between the frame sides. Two outer backup rolls centered on parallel axes transverse to the direction are spaced vertically apart and each have two journal blocks vertically displaceable and guided in the windows of the respective frame sides. Respective upper and lower guide elements limitedly vertically displaceable in the windows between the outer-roll journal blocks carry the journal blocks of two inner backup rolls centered on parallel axes between and coplanar with the outer-roll axes. Respective pairs of positioning actuators in the windows vertically between the respective inner-roll blocks have actuators which confront each other in the direction and are oppositely braced in the direction against the respective frame side. Respective supports carried on and between the actuators of each pair themselves carry respective upper and lower guide elements limitedly vertically displaceable on the supports. The positioning actuators are expansible and contractile to displace the guide elements in the direction. Two working rolls centered on parallel axes between and parallel to the other roll axes each have two journal blocks fitted to and axially slidable in the respective journal blocks. Thus the positioning actuators can position the working rolls in the direction. An insert is carried in the traverses axially between and secured to the positioning actuators upstream of the roll-axis plane. Respective rows of bracing rollers are carried on the insert and extend axially along the working rolls between same and the traverses. The insert, bracing rollers, and upstream positioning actuators form an integral bracing unit and at least one of the windows is shaped such that the bracing unit can be withdrawn axially through the respective frame side. Respective rows of bracing actuators braced in the direction between the rollers and the traverses can displace the rollers through at least 50 mm in the direction and press the rollers opposite to the direction against the respective working rolls. Normally the inner backup rolls are axially displaceable with the respective journal blocks in the frame.
These positioning actuators that are braced via the respective supports and guide elements between the respective working-roll journal blocks and the confronting faces of the windows of the roll frame must be as short as possible in the workpiece travel direction so the windows do not have to be so wide that the frame is weakened. In addition they must be capable of exerting enormous forces, while applying no torsion to the elements they lie between as canting of the guide elements could impede proper machine operation. Finally, such devices should be capable of accurately moving into a set position and holding it perfectly.
The standard solution is one or more squat rams. Although such an arrangement does fit in with the normally hydraulic controls of a roll stand, it still requires extensive control technology, and due to the high pressures employed is a fairly expensive item.
Mechanical means such as wedges have been employed also, but these arrangements have the disadvantage of causing the controlled element to shift somewhat as there is a vector of force involved that does not run parallel to the positioning direction which is parallel to the workpiece-travel direction, and normally they are driven by threaded spindles that exert an appreciable torque on the entire actuator.